1. Field of the Invention
This invention relates to a wear-resistant film and more particularly to a wear-resistant film having an aluminum oxide film formed on a surface of a substrate made of aluminum or an aluminum alloy (hereinafter referred to as "aluminum alloy substrate") through the medium of a silicon oxide film.
2. Description of the Prior Art
It is known that an aluminum oxide film manufactured by a sputtering process has a low friction coefficient and relatively large durability to resist friction as compared with films of such other ceramic substances as TiC, TiN, BN, and SiO.sub.2. Thus, the adoption of the aluminum oxide film as a surface protecting film (wear-resisting film) for aluminum alloy building materials, personal ornaments made of aluminum alloy (such as watches), machine parts, and the like has been contemplated.
Such surface protecting films as wear-resistant films are generally required to excel in adhesiveness to substrates.
The formation of a wear-resistant film on an aluminum alloy substrate is generally carried out by directly superposing an aluminum oxide film on the aluminum alloy substrate. The aluminum oxide film formed by this method, however, does not exhibit satisfactory adhesiveness to the aluminum alloy substrate and entails the possibility of being peeled off the substrate under high load and cannot be expected to manifest excellent wear resistance.
In the circumstances, a technique which is capable of forming an aluminum oxide film exhibiting high adhesiveness to an aluminum alloy substrate has long been desired.